Cyclooxygenase-2 (COX-2) is overexpressed in a majority of pancreatic tumors, but the biological significance of this phenomenon remains unclear. Our preliminary data suggest that the epidermal growth factor receptor (EGF-R) and the receptor for platelet-activating factor (PAF) coordinately maintain COX-2 expression in human pancreatic cancer cell lines. Furthermore, our results indicate that COX-2 promotes cell survival by antagonizing the pro-apoptotic effects of arachidonic acid. Together, these results serve as the basis for our hypothesis that arachidonic acid metabolites play a central role in maintaining high level COX-2 expression in pancreatic cancer, which functions to antagonize the cytotoxic effects of arachidonic acid. Here we propose to extend these observations in Aim 1 by identifying the signaling and transcriptional mechanisms underlying COX-2 expression in our cell lines, focusing on the pathways that converge on AP-1 and CREB. In Aim 2 we will characterize the biochemical mechanism(s) involved in arachidonic acid-induced apoptosis (with a focus on ceramide) and identify the survival signal(s) controlled by COX-2. Finally, in Aim 3 we will study the effects of inhibitors of COX-2 (Celebrex) and the EGF-R (OSI-774) in orthotopic models of human pancreatic cancer on target inhibition, apoptosis, and inhibition of angiogenesis. We will then use the information gained from the studies to evaluate drug-target interactions and other surrogate biological markers of response in a clinical trial of Celebrex plus OSI-774 in pancreatic cancer patients. Analysis of the regulation and biological function(s) of COX-2 in pancreatic cancer should help us to identify new targets for therapeutic intervention. Identification of biological surrogates of drug targeting should allow us to best exploit the therapeutic potential of existing agents that target these important pathways.